Studies on the Modification of Commercial Epoxy Resin using Cardanol-based Phenolic Resins

摘要

Bisphenol A epoxy resin is blended with different phenolic novolac resins for property modification.The phenolic resins employed are (a) novolac resins derived from phenol/formaldehyde (PN) and cardanol/ formaldehyde (CDN) condensation and (b) condensation products of cardanol-phenol mixtures with formaldehyde (CPNs).Cardanol is the main constituent of cashew nut shell liquid (CNSL),a renewable resource.Epoxy resins containing 2.5-20 wt% of the above novolacs are prepared and tested for mechanical properties,water absorption,etc.Blends containing 5-10 wt% of novolacs show substantial improvement in properties.These properties show a declining trend with higher novolac loading.The stoichiometric ratio between phenolic material and formaldehyde in the novolacs is optimized (1:0.8) for maximum property enhancement.Among the novolacs studied,those prepared from cardanol-phenol mixtures of different molar ratios (CPNs) yield comparatively higher energy absorption at break and this property increases with increase in cardanol content in the modifier resin up to 40%.The property profiles of these epoxy-novolac blends imply a toughening action by novolac resins,especially phenol-cardanol-formaldehyde resins.